Sensor and package

ABSTRACT

A fluid sensor comprises a formed plastic body and a reagent. The body has a top face with an integral first surface. The body also has a bottom face opposed to the first surface and a sidewall that extends from the periphery of the top face. The first surface is adapted to accept a fluid sample. The reagent is disposed on the integral first surface and causes a color change detectable on the bottom face when the reagent reacts with an analyte in the fluid sample.

TECHNICAL FIELD

The present invention relates to a fluid monitoring system, and moreparticularly, to a new and improved sensor and package that is used inanalyzing blood glucose or other analytes contained therein.

BACKGROUND

Those who have irregular blood glucose concentration levels aremedically required to regularly self-monitor their blood glucoseconcentration level. An irregular blood glucose level can be brought onby a variety of reasons including an illness such as diabetes. Anestimated 18 million people are afflicted with diabetes in the UnitedStates alone. A diabetic patient typically monitors his or her bloodglucose concentration level to determine whether the level is too highor too low, and whether any corrective action, such as administeringinsulin or other medication, is necessary to bring the level back withina normal range. The failure to take corrective action can have seriousimplications. When blood glucose levels drop too low—a condition knownas hypoglycemia—a person may become nervous, shaky, confused, have animpaired judgment, and eventually pass out. A person can also becomevery ill if their blood glucose level becomes too high—a condition knownas hyperglycemia. Both hypoglycemia and hyperglycemia can potentially belife-threatening emergencies. As a result, a diabetic may requirefrequent sampling of his or her blood glucose—typically several timesper day.

In one type of blood glucose testing system, sensors are used to test asample of blood. Such a sensor may contain bio-sensing or reagentmaterial that will react with blood glucose. The testing end of thesensor is adapted to be placed into the fluid being tested, for example,blood that has accumulated on a person's finger after the finger hasbeen pricked. In one type of sensor, for example in U.S. Pat. No.5,100,620, issued Mar. 31, 1992, and entitled Capillary Tube/Gap ReagentFormat, the fluid is drawn into a capillary channel that extends in thesensor from the testing end to the reagent material by capillary actionso that a sufficient amount of fluid to be tested is drawn into thesensor. For electrochemical sensors, the fluid then chemically reactswith the reagent material in the sensor. The chemical reaction resultsin an electrical signal indicative of the blood glucose level in theblood being tested, which is then supplied to contact areas located nearthe rear or contact end of the sensor. For optically read or photometricsensors, a reflectance reading can determine the color change indicativeof the glucose concentration in the blood/reagent mixture.

As with all medical diagnostic devices, contamination is of majorconcern. It is necessary to avoid contamination of both equipment andpersonnel by fluids, and to avoid contamination of a patient with fluidsfrom others. For photometric blood glucose monitors in particular, amajor concern is contamination of the read-head by blood. Blood on theoptical read-head can give rise to erroneous measurements. To addressthis problem, current sensors have been designed so that they areinoculated with a patient's blood before the sensor is placed in themeter. While this configuration reduces the risk of contamination forthe patient, the meter can still become contaminated with blood. Inaddition, this process is less convenient for the user.

To address the risk of meter contamination, some sensors have beendesigned to include a reactive membrane stretched across a throughopening in a shaped sensor tip. While such sensors reduce the risk ofmeter contamination over conventional sensors, there still remains therisk that the read-head of the meter can become contaminated. Thereactive membrane does not completely cover the through opening,allowing the possibility that blood may leak onto the meter or read-headeither through the membrane or around the membrane/through openingjuncture.

Manufacturing cost is another concern that exists with sensors thatinclude a reactive membrane stretched across a through opening. Due tothe large number of sensors a diabetic may use, even a minor reductionin the manufacturing cost of a sensor can result in substantial savingsto the diabetic end user. Applying a separate membrane to a throughopening involves extra manufacturing steps of handling a separatemembrane and applying the membrane to the sensor base.

In addition to cost, reducing the sample volume is another concern thatexists for current sensors. Current sensors require sample volumesanywhere from approximately 0.3 μL to 10.0 μL of blood. For example, inconventional capillary fill sensors, it is difficult to get a reasonableseparation between the sample application point on the sensor and theread-head. To illustrate this, if the sensor protrudes 0.3 inches fromthe meter and the read-head is located 0.2 inches inside the meter case,then the capillary must be 0.5 inches long. Aside from resulting in aconsiderable waste of sample, this can also lead to a slow fill time andrequire larger punctures to extract the necessary quantity of blood.

Another challenge with current sensors is their packaging. Before use,the sensors need to be maintained at an appropriate humidity level so asto insure the integrity of the reagent materials in the sensor. Sensorscan be packaged individually in tear-away packages so that they can bemaintained at the proper humidity level. For instance, blister-typepackaging methods have often been used. The packages can includedesiccant material to maintain the proper humidity in the package. Inorder for a person to use an individual sensor for testing bloodglucose, the package must be opened by tearing the seal. Alternatively,some packages require the user to exert force against one side of thepackage resulting in the sensor bursting or rupturing the foil on theopposite side. As can be appreciated, the opening of these packages canbe difficult and may result in damage to the sensor. Moreover, once thepackage is opened the user needs to be sure that the sensor is notdamaged or contaminated as it is being placed into the sensor holder andused to test the blood sample.

Other sensor packages, such as the one used in U.S. Pat. No. 5,630,986,issued May 20, 1997, and entitled Dispensing Instrument for FluidMonitoring Sensors, also maintain a low humidity environment, but theyare not easy to manufacture. One reason is that the symmetry of thecircular packaging array does not match the rectangular symmetry ofstandard sheet sensor printing processes, necessitating handlingindividual sensors during packaging. The meter is also mechanicallycomplex because of the mechanism required to extract the sensor from theblister pack. In addition, the number of sensors is not visible at aglance.

For the foregoing reasons, there is a need for a blood glucose sensorthat reduces the risk of contamination, the manufacturing cost, and thesample volume. Further, there is a need for a package for such a bloodglucose sensor that maintains the sensors at the proper humidity, issimple to use, and has a visual display of the remaining sensors.

BRIEF SUMMARY

Accordingly, an object of the present invention is to provide a new andimproved sensor and package used in testing blood glucose. Inparticular, objects of the present invention are to provide a new andimproved blood glucose sensor and package made from a one-piece formedbody with a reagent applied to the sensor, and which overcomes theproblems or limitations discussed above.

In accordance with these and other objects of the present invention, thepresent invention is embodied in a fluid sensor that comprises a formedplastic body and a reagent. The body has a top face with an integralfirst surface. The body also has a bottom face opposed to the firstsurface and a sidewall that extends from the periphery of the top face.The first surface is adapted to accept a fluid sample. The reagent isdisposed on the integral first surface and causes a color changedetectable on the bottom face when the reagent reacts with an analyte inthe fluid sample.

In a second embodiment of the present invention, a fluid sensorcomprises a formed porous plastic body, a surfactant, and a reagent. Thebody has a top face with an integral first surface, a bottom face with asecond surface opposed to the first surface, and a sidewall adjacent tothe top face. The first surface is adapted to accept a fluid sample. Thesurfactant is disposed on the body. The reagent causes a color changedetectable on the second surface when the reagent reacts with an analytein the fluid sample.

In accordance with a third aspect of the present invention, the presentinvention is embodied in a blood glucose sensor kit comprising a sensorpackage, a blood glucose meter, and a guide. The sensor package includesa base portion having at least one sensor cavity and at least onedesiccant cavity in fluid communication with the sensor cavity. Thesensor package also includes a desiccant material in the desiccantcavity and a protective sheet covering the sensor cavity and thedesiccant cavity. The sensor package also includes a sensor located inthe sensor cavity. The blood glucose meter has a housing, a displaydisposed on the housing, and a read-head disposed on the housing, inwhich the read-head is adapted to detachably engage the sensor. Theguide is adapted to cover the protective sheet. The guide also has atleast one opening adapted to align the read-head to engage the sensorwithin the sensor cavity.

According to a fourth aspect of the present invention, a blood glucosesensor kit comprises a sensor package and a blood glucose meter. Thesensor package includes a container having an inner surface, a desiccantliner disposed in the container, a friction liner disposed in thecontainer, and at least one sensor located in the container,frictionally engaging the friction liner. The blood glucose meter has ahousing with a display and a read-head disposed on the housing. Theread-head is adapted to detachably engage the sensor while the sensor islocated in the sensor package.

According to a fifth aspect of the present invention, a blood glucosesensor package comprises a container, a desiccant liner, a frictionliner, a first sensor, and a cover. The container has an inner surface.The desiccant liner is disposed in the container. The friction liner isdisposed in the container. The first sensor is located in the containerand frictionally engages the friction liner. The cover seals thecontainer.

According to a sixth aspect of the present invention, a method of makinga fluid sensor includes the act of forming a plastic body. The plasticbody has a top face with an integral first surface, a bottom faceopposed to the first surface, and a sidewall extending from theperiphery of the top face. The first surface is adapted to accept afluid sample. The method also includes the act of applying a reagent tothe integral first surface. The reagent causes a color change detectableon the bottom face when the reagent reacts with an analyte in the fluidsample. The method also includes the act of applying a lid to a raisedregion on the top face.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a blood glucose sensor constituting oneembodiment of the present invention.

FIG. 2 is a partial cross-section view of the blood glucose sensor ofFIG. 1.

FIG. 3 is a perspective view of a blood glucose sensor constituting asecond embodiment of the present invention.

FIG. 4 is a partial cross-section view of the blood glucose sensor ofFIG. 3.

FIG. 5 is a perspective view of a blood glucose sensor constituting athird embodiment of the present invention.

FIG. 6 is a cross-section view of the blood glucose sensor of FIG. 5.

FIG. 7 is a perspective view of a fourth embodiment of the presentinvention, illustrating a shoulder on the sidewall of the blood glucosesensor.

FIG. 8 is a cross-section view of the blood glucose sensor of FIG. 7.

FIG. 9 is an exploded perspective view of a blood glucose kit.

FIG. 10 is a top perspective view of a sensor package used with theblood glucose meter of FIG. 9.

FIG. 11 is a partial cross-section view of a read-head of a bloodglucose meter inserted into the sensor of FIG. 7 contained within asensor package.

FIG. 12 is a side perspective view of another sensor package.

FIG. 13 is a cross-section view of the sensor package of FIG. 12.

FIG. 14 is a partial cross-section view of another blood glucose kit andthe sensor package of FIG. 12.

FIG. 15 is a partial cross-section view of an alternate blood glucoseinstrument and the sensor package of FIG. 12.

FIG. 16 is a cross-section view of an array of the blood glucose sensorsof FIG. 1, illustrating a sequence of steps in the typical constructionof the sensors with integral spacers.

FIG. 17 is a cross-section view of an array of the blood glucose sensorsin FIG. 3, illustrating a sequence of steps in the typical constructionof the sensors with spacers made by printing.

DETAILED DESCRIPTION OF THE DRAWINGS AND THE PRESENTLY PREFERREDEMBODIMENTS

Referring now more specifically to the drawings, therein is disclosed afluid sensor generally designated by the reference numeral 10 andembodying the present invention. As illustrated in FIGS. 1-2, oneembodiment of the sensor 10 includes a body 12, a reagent 30, and a lid40.

The body 12 may be formed into a hollow frustum (such as a conical orpyramidal shape) shaped to mount on an optical read-head 510 ofcorresponding shape (FIGS. 9 and 11). The read-head 510 can host twolight guides, one for alight source and another for reflected light.Body 12 may be formed from impermeable plastic such as polypropylene,polyethylene terephthalate, or other plastic, using techniques known inthe art, such as film forming, injection molding, etc. The frustumshaped body 12 has only one open end, with integral sidewalls 14 thatextend downward from the periphery of a top face 16. A bottom face 18 islocated on the inside of body 12, opposite top face 16. Body 12 may besized with an overall height of 0.2 inches, although other heights thatare sufficient to avoid contamination of a glucose meter 502 by sampleblood may also be used.

The engagement of body 12 with the read-head 510 can be facilitated by afirst latch 24 located on the sidewall 14 of the sensor. The latch 24may be formed using any technique known in the art and may comprise anynumber of shapes, such as indentations, holes, grooves, or embosses inthe sidewall 14 of body 12.

The top face 16 has a raised region forming a spacer 22 that surroundsan integral first surface 20, which may be formed into a concave orrecessed surface for ergonomic sample loading. In the embodiment shownin FIGS. 1-2, spacer 22 is depicted as an annulus, although other shapesmay be used. Spacer 22 may be integrally formed with body 12.Alternately, spacer 22 may be formed as a separate molded spacer andattached to the top face 16 of body 12 through sonic welding, anadhesive, or other method of attachment.

Lid 40 is mounted to spacer 22 on the top face 16 of body 12, forming acapillary chamber 50. As best seen in FIG. 1, this arrangement has opensides formed by the gap between lid 40 and first surface 20 so as toprovide access by a blood sample to the capillary chamber 50. Capillarychamber 50 allows for a controlled sample volume of blood to react withreagent 30. FIGS. 1 and 2 illustrate one embodiment where lid 40 isconstructed of a rectangular strip of impermeable plastic, formed in asimilar manner to body 12 described above. However, lid 40 is preferablycolored to form an opaque barrier as described below. In addition, othershapes for lid 40, such as a circle, square, etc. may also be used.Similarly, spacer 22 may be formed such that it is only under the lid40, and does not form a complete raised ring around top face 16 of body12. Lid 40 may be attached to spacer 22 through sonic welding, anadhesive, or other attachment method.

Reagent 30 is applied to the first surface 20 such that when a dropletof blood is applied to first surface 20, the blood reacts with thereagent 30. Reagent 30 causes a color change that can be detected byread-head 510 from bottom face 18. As a result, top face 16 of body 12is colored to allow sufficient light to be transmitted from firstsurface 20 to bottom face 18. For example, top face 16 may have atranslucent or transparent coloring. To reduce manufacturing costs,reagent 30 may be applied directly to the plastic of body 12 through acoating, screen, or stencil-printing process. Alternatively, methodssuch as pipetting, pump deposition, or pin deposition can be used. Ifthe reagent 30 is applied to the first surface 20 through pipetting orpump or pin deposition, improved results may be obtained if the reagentaccepting surface has an area defined by a raised mesa. Reagent 30 mayalso be membrane-based, however, in another embodiment.

The reagent 30 may be made from any of a number of compositions that arecapable of generating detectable specie that can be measured by a changein reflectance. One such reagent composition is a glucose dehydrogenase(GDH)-pyrroloquinoline quinone (PQQ) based system. Such a reagent systemis described as follows:

-   -   1) glucose+GDH-PQQ (oxidized state)→gluconolactone+GDH-PQQ        (reduced state)    -   2) electron transferring mediator (oxidized state)+GDH-PQQ        (reduced state)→electron transferring mediator (reduced        state)+GDH-PQQ (oxidized state)    -   3) electron transferring mediator (reduced        state)+tetrazolium→electron transferring mediator (oxidized        state)+formazan        The intensity of the color of formazan, which is measured by a        photometric sensor (not shown) in read-head 510, is a function        of the concentration of glucose. Alternatively, a GDH and        diaphorase based system can be used. Such a system is described        as follows:

The reagent 30 compositions can be deposited onto the first surface 20of body 12 in a matrix, such as a titanium dioxide and polymer (e.g.,polyacrylic) matrix, according to any of the methods described above.

In operation, the sensor 10 is mounted to read-head 510 on the bloodglucose meter 502. Blood glucose meter 502 (seen in FIG. 9) takes aninitial reflectance reading on sensor 10 prior to the application of ablood sample to the sensor 10. This initial reading serves to correctfor variations in background color and sensor positioning. A user isthen prompted to apply a blood sample to lid 40. The blood sample isdrawn by capillary action into capillary chamber 50 to react withreagent 30. After a predetermined period of time, blood glucose meter502 then takes another reflectance reading of sensor 10. Thisreflectance reading of reagent 30 on sensor 10 measures the color changeof formazan or other detectable specie, which indicates the glucoseconcentration in the blood/reagent mixture.

Because the detectable specie generated from the analyte is measured bya change in reflectance, a significant fraction of light is transmittedthrough the reagent 30 where it can be lost or returned to the read-head510 by scattering from the blood sample. The amount of light scatteringdepends on the sample volume and hematocrit, which may lead toinaccuracies in the reflectance measurement. Further, if the bloodvolume sample above the reagent 30 is not defined, the conversionreaction continues past the ideal test time. This leads to drifting ofthe result. Capillary chamber 50 is designed to serve as a reactioncell, providing a defined volume and surface on the side opposing thereagent 30. In addition, lid 40 preferably has an opaque coloration toprovide a defined and consistent reflective background.

FIGS. 16 and 17 illustrate two construction methods for an array ofsensors 10 with capillary chambers 50 as described above. In FIG. 16,the spacer 22 is integrally molded with the body 12. The reagent 30 isthen applied to the first surface 20, in the area between spacer 22, asdescribed above. The lid 40 is applied next. The surface of the lid 40that faces the inside of the capillary chamber can be optimized forrapid filling and may also be a heat-activated adhesive, such as U53water dispersible polyurethane available from Bayer Corporation ofElkhart, Ind., United States of America. This lid formulation is knownas ROA. The lid is temporarily mounted to a backing adhesive 41 anddie-cut in this form, through the ROA but leaving the temporary backing41 intact. This structure is aligned over the tips as shown and heatedthrough the temporary backing 41 to adhere the ROA adhesive to thespacers 22 of the sensor 10. Finally the temporary backing 41 is removedleaving completed sensors 10.

FIG. 17 shows a variation of the construction method depicted in FIG.16. Body 12 is molded without an integral spacer 22. The flat top of thebody 12 is advantageously suited for screen or stencil-printing thespacer 22. Alternatively, spacer 22 may be made in a printing step. Toavoid a heat sealing step when applying the lid 40, a hydrophilicpressure-sensitive adhesive may be used instead.

Another embodiment of a sensor 60 is illustrated in FIGS. 3 and 4.Sensor 60 includes body 12, reagent 30, and a sensor lid 45. Sensor lid45 may be formed from impermeable plastic as a hollow frustum, similarto body 12, as described above. Sensor lid 45 may be attached to bodythrough a second latch 48 located on a sidewall 49 of sensor lid 45. Thesecond latch 48 may comprise any technique known in the art, such asindentations, holes, grooves, or embosses. Alternately, sensor lid 45may be attached to body 12 through sonic welding, an adhesive, oranother attachment method. Vent holes 46 are formed in sensor lid 45 toallow a blood sample to flow into capillary chamber 51 and air to flowout of chamber 51 formed by the sensor lid 45 and the body 12. Otheraspects of the sensor 60 are similar to the sensor 10 shown in FIGS. 1and 2 and described above.

Another embodiment of a sensor 70 is illustrated in FIGS. 5 and 6.Sensor 70 is made up of a body 112 and reagent 30, but does not includea lid or sensor lid (as those components are described in connectionwith the embodiments of FIGS. 1-4). Although a significant fraction oflight may be lost and the blood volume sample above the reagent 30 maynot be defined, blood glucose meter 502 may be adapted to correct forthis by taking additional reflectance readings or with some othercorrection. Other aspects of sensor 70 are similar to the sensor 10shown in FIGS. 1 and 2 and described above.

In another embodiment of the present invention, illustrated in FIGS. 7and 8, the body 90 comprises a porous plastic. The porous plastic ofbody 90 may be formed similarly to the impermeable plastic of body 12,as described above in connection with the embodiments of FIGS. 1 and 2.The porous plastic is a sintered polymer such as polypropylene,polyvinylidene fluoride, polyethylenevinyl acetate,polystyreneacrylonitrite, polytetrafluoroethylene or related copolymers.The porous plastic may also be opaque, to reduce the amount of lighttransmitted through it and increase the amount of light reflected fromthe sample. The pore size may range from 5 to 100 microns, althoughother sizes may be used. The porous plastic is hydrophobic so that itresists sample flow unless first treated with a surfactant (not shown).Surfactant may be applied to a sample surface 94 on the outside tipsurface 95 of the tip of body 90. Alternately, surfactant may be appliedto the inside tip surface 96 of the body 90. To prevent uncontrolledsample flow within the body 90, however, only the reactive area ispreferably treated with surfactant. Typical surfactants are derivativesof polyethylene glycol ester, polysorbate, or sorbitan ester.

Sample surface 94 accepts a sample, and can be formed into a concavesurface for ergonomic sample loading. A sidewall 97 may extend aroundthe periphery of sample surface 94. A reagent 30, as described above, isapplied to the body 90 such that when a droplet of blood reacts with thereagent 30, a color change is caused that can be detected from theinside tip surface 96 of body 90. As illustrated in FIG. 8, the reagent30 is affixed to the inside tip surface 96 of body 90, opposite samplesurface 94. Alternately, the reagent 30 may be affixed to sample surface94, with surfactant applied to the inside tip surface 96 of body 90.Other aspects of the sensor 90 are similar to the sensor 10 shown inFIGS. 1 and 2 and described above.

FIG. 9 illustrates a blood glucose sensor kit 500 comprising the bloodglucose meter 502, a sensor package 550 containing the sensors 10described above, an alignment guide 540, and an optional removable bloodglucose meter cover 530. The blood glucose meter 502 comprises a housing504, a display 506 for depicting the analyte concentration measured bythe meter 502, an optical read-head 510 disposed on the housing 504, anda spring-loaded lancet mechanism 520. As described above, read-head 510comprises a shape that corresponds to the shape of the sensor 10. Anengagement mechanism, such as a push-button ejection mechanism, islocated on read-head 510 to detachably engage sensor 10 through firstlatch 24.

As best seen in FIGS. 10-11, the sensor package 550 comprises a baseportion 552, a desiccant material 557, and a protective sheet 558.Sensor cavities 554 are formed as depressions in the base portion 552,with each of the sensor cavities 554 adapted to house an individualsensor 10. As seen in FIG. 11, to prevent or inhibit movement of sensor10 in the sensor cavity 554, the sensor cavity 554 has an inclined orsloped support wall to position the sensor 10 while it is disposedwithin the sensor cavity 554. Each of the sensor cavities 554 is influid communication with a desiccant cavity 556 formed by a smalldepression in the base portion 552. Desiccant material 557, such as a 6mg sphere of Grace 10A molecular sieve desiccant, is disposed in each ofthe desiccant cavities 556 to maintain an appropriate humidity level topreserve the reagent 30 on the sensor 10. The sensor cavities 554 anddesiccant cavities 556 may be aligned in rectangular arrays, allowingfor reduced manufacturing and packaging costs.

The protective sheet 558 is attached to base portion 552 such that itseals the individual sensor cavities 554 and desiccant cavities 556,providing a moisture barrier so that the desiccant material 557 canmaintain the relative humidity within an optimal range. FIG. 11illustrates a sensor package 550 design intended for aluminum foil asthe protective sheet 558. The sensor cavity 554 is closed byheat-sealing an aluminum burst foil to the surface of the base foil. Atypical configuration of this foil is a laminate consisting of alacquer/8 μ aluminium/10 μ polypropylene heat-seal material, with anexpected shelf life of one to two years for this configuration. One typeof foil that can be used for the protective sheet 558 is AL-191-01 foildistributed by Alusuisse Flexible Packaging, Inc. With a tip height of0.247 inches and a seal width of 0.088 inches, the maximum elongation ofthe foil is estimated to be 36%.

A conductive calibration label 559 is also disposed on the sensorpackage 550. The conductive calibration label 559 can be locatedanywhere on sensor package 550 that space and size constraints allow,for example, on protective cover 558 or on base portion 552. Theconductive calibration label 559 provides calibration and productioninformation about the sensor package 550 that can be sensed bycalibration circuitry in the blood glucose meter 502. Additional detailsregarding sensor package 550 are described in U.S. Pat. No. 5,575,403,issued Nov. 19, 1996, and entitled Dispensing Instrument For FluidMonitoring Sensors, the contents of which are hereby incorporated byreference. One example of such a sensor pack is the Ascensia® AUTODISC™with ten test strips also available from Bayer Corporation of Elkhart,Ind., United States of America.

Alternatively, sensor package 550 may use a protective sheet 558 madefrom a thermoformed plastic barrier material. With a thermoformedplastic barrier material, a much greater degree of elongation or stretchis possible. This allows for a more compact package while alsoaccommodating a taller sensor (approximately 0.2″ tall). Formablepackaging material is available from Klockner-Pentaplast, for examplePentapharm ACLAR PA 300/2. The product, containing ACLAR Ultrx3000, hasa Moisture Vapor Transfer Rate (MVTR) of 0.005 g/100 sq in/day at 38° C.and 90% Relative Humidity. With a 6 mg desiccant bead having 15% ofavailable moisture capacity, the expected lifetime of the sensor package550 is about 45 days.

Referring to FIG. 9, alignment guide 540 is used because the sensors 10are invisible behind the burst toil of the protective sheet 558.Alignment guide 540 serves to align the read-head 510 with the sensor10. As shown in FIG. 11, the read-head has two levels of taper, with astep between the two sections. The smaller diameter section 512 of theread-head engages directly with the sensor 10. The larger diametersection 514 is sized to interact with the holes 542 in alignment guide540 to correctly position the read-head 510 over the sensor 10. A stepbetween the two sections of the read-head 510, with the diameter at thetop of the step being slightly larger than the diameter at the base ofthe sensor, serves to prevent or inhibit the sensor from being caught onthe alignment guide as the read-head and attached sensor are withdrawnfrom the sensor package.

Removable meter cover 530 detachably mounts to blood glucose meter 502,covering the read-head 510 and lancet mechanism 520. The removable metercover 530 also has a recess adapted to contain the sensor package 550and alignment guide 540.

To operate a typical blood glucose meter kit 500, the sensor package 550is stored in the removable meter cover 530 of the blood glucose meter502 underneath the alignment guide 540 with the calibration label 559exposed at one end. The sensor package 550 is keyed to ensure thecorrect orientation within the removable meter cover. Before use, theremovable meter cover 530 is removed and the read-head 510 is pusheddown through the alignment guide 540 into the sensor package 550 beneathto engage and pick up a sensor 10. The lancet mechanism 520 on the meter502 is then used to draw a blood droplet that is subsequently applied tothe integral first surface 20 of the sensor 10 to start the measurementsequence. After the sequence is completed, the blood glucose measurementis displayed on the meter display 506, the sensor 10 is ejected, and thecover 530 is replaced. With the number of remaining sensors 10 beingvisible at a glance, an empty sensor package 550 can be easily replacedby raising the alignment guide 540 and removing it from the removablemeter cover 530.

FIG. 12 illustrates another embodiment of a sensor package 650 forstoring a plurality of sensors 90. As seen in FIG. 13, sensor package650 comprises a container 652 with an inner surface 654, and a cap 656capable of detachably sealing the container 652. An optional hinge 658may be connected to the cap 656 and container 652 to allow the cap toopen in a flip-top manner. Alternatively, the cap 656 can be fastened tocontainer 652 as a push-on cap, a threaded cap, or by other knownmethods of attachment. In addition, cap 656 may be a heat sealed orother type of single use lid. A desiccant liner 662 is disposed insidecontainer 652 to maintain an appropriate humidity level to preserve thereagent 30 on the sensor 90. Preferably, desiccant liner 662 is appliedto inner surface 654, but may be located anywhere within container 652.A friction liner 664 is also disposed within container 652 so that aplurality of stacked sensors 10 frictionally engages the friction liner664. Preferably, friction liner 664 is applied to the inner surface ofdesiccant liner 662 and may be made from any friction material,including any elastic, rubber-like material. Friction liner 664 isintended to exert gentle pressure on the edges of a sidewall 97 toprevent or inhibit movement of the sensors 90 while being engaged byread-head 510. The sensor package 650, depicted as a bottle in FIGS. 12and 13, may be relatively compact. The embodiment illustrated is sizedto hold twenty sensors 90 in a nested array, with a 2 inch height and0.46 inch diameter, but may be sized to house other numbers or sizes ofsensors.

FIG. 13 illustrates a plurality of sensor bodies 90 of FIGS. 7 and 8positioned within sensor package 650. As described above, sensor body 90has stepped sidewall 97 such that a shoulder 99 is formed. The shoulder99 allows sensor body 90 to nest inside another sensor body 90,ultimately forming a nested vertical array of sensors. It should beunderstood that sensor package 650 may also be used to store the othersensor embodiments disclosed above.

To attach a sensor 90 to the read-head 610, 710 of meter 602, 702 (seenin FIGS. 14 and 15), read-head 610, 710 is pushed down onto a stack ofsensors 90 until the latch 98 on the sensor mates with the engagementmeans (not shown) on the read-head 510. The read-head 510 is thenwithdrawn with a sensor 90 loaded ready for inoculation with blood.Because of the downward pressure on the stack during mounting, there isa tendency for the sensors to stick together, with the conical outersurface of one sensor binding with the matching conical inner surface ofthe sensor below. The shoulder 99 of sensor body 90 rests on the top ofthe sensor body 90 below, and is designed to avoid this binding ofsuccessive sensors.

FIG. 15 illustrates a meter 702 with read-head 710 and a cover (notshown) removed. The meter 702 is adapted to be used with sensor package650. For meter 702, sensor package 650 is stored separately from meter702. The meter 702 contains a bottle cavity 704 concentric with theread-head 710, allowing the read-head 710 to reach down to the bottom ofthe sensor package 650 and pick out the last sensor 10. A slot (notshown) may also be formed in meter 702 to run almost the length of thebottle cavity 704 to accept the hinge of the bottle. A scribe 706 ispositioned on meter 702 to leave a mark on a label 670 that indicatesthe number of sensors remaining within sensor package 650. The scribe706 provides for a convenient, instantly visible method of estimatingthe number of sensors remaining in sensor package 650.

FIG. 14 illustrates another meter 602 with read-head 610 and a cover 630adapted to store sensor package 650. The meter 602 has two recesses, abottle cavity 604 concentric with the read-head 610 (described above),and a storage recess 606. When not in use, sensor package 650 is storedwithin storage recess 606 of the meter 602. A spring-loaded cap (notshown) within the meter 602 seals to the open sensor package 650 toensure a moisture-proof seal. In operation, to load a sensor 10, thecover 630 is removed from meter 602, rotated 180 degrees and thenreplaced onto the meter 602, bringing the read-head 610 down into thesensor package 650. After the test is complete (described above), thesensor 10 is ejected and the cover 630 is replaced to seal the sensorpackage 650 in the storage recess 606. Meter 602 may also position ascribe 608 to leave a mark on a label 670 that indicates the number ofsensors remaining within sensor package 650, as described above.

While the invention has been described with reference to details of theillustrated embodiments, these details are not intended to limit thescope of the invention as defined in the appended claims. For example,the sensor may be used for testing fluids other than blood glucose. Infact, the sensor can be used in connection with the analysis of any typeof chemical fluid that can be analyzed by means of a reagent material.In addition, the sensors may use sizes, shapes, angles, etc. differentthan those described above. Further, porous or impermeable plastic bodydesigns may be used with any of the sensor shapes described in FIGS.1-8. A sensor lid or lid may also be used with porous designs. Moreover,except as noted above, the coloration of the sensor body may be alteredsuch that it is transparent, translucent, or opaque. It is thereforeintended to include within the invention all such variations andmodifications that fall within the scope of the appended claims andequivalents thereof.

Alternative Embodiment A

A fluid sensor comprising:

a formed plastic body having a tap face with an integral first surface,a bottom face opposed to said first surface, and a sidewall extendingfrom the periphery of said top face, said first surface being adapted toaccept a fluid sample; and

a reagent, being disposed on said integral first surface and adapted tocause a color change detectable on said bottom face when said reagentreacts with an analyte in said fluid sample.

Alternative Embodiment B

The sensor of alternative embodiment A wherein said formed plastic bodyis a hollow frustum.

Alternative Embodiment C

The sensor of alternative embodiment A wherein said formed plastic bodyis a hollow frustum with a larger open end and a smaller closed end.

Alternative Embodiment D

The sensor of alternative embodiment A wherein said sidewall has atleast one latch.

Alternative Embodiment E

The sensor of alternative embodiment D wherein said at least one latchis an indentation, hole, groove, or emboss.

Alternative Embodiment F

The sensor of alternative embodiment A wherein said sidewall forms ashoulder.

Alternative Embodiment G

The sensor of alternative embodiment A wherein said color change ismeasured by a change in reflectance on said bottom face.

Alternative Embodiment H

The sensor of alternative embodiment G wherein said reagent is a glucosedehydrogenase and pyrroloquinoline quinone-based system.

Alternative Embodiment I

The sensor of alternative embodiment H wherein said reagent furthercomprises an electron transferring mediator, tetrazolium, and formazan.

Alternative Embodiment J

The sensor of alternative embodiment G wherein said reagent is a glucosedehydrogenase and diaphorase-based system.

Alternative Embodiment K

The sensor of alternative embodiment J wherein said reagent furthercomprises nicotinamide adenine dinucleotide, tetrazolium, and formazan.

Alternative Embodiment L

The sensor of alternative embodiment H wherein said reagent is atitanium dioxide and polymer matrix.

Alternative Embodiment M

The sensor of alternative embodiment I wherein said reagent is atitanium dioxide and polymer matrix.

Alternative Embodiment N

The sensor of alternative embodiment C wherein said frustum has acircular or rectangular cross-section.

Alternative Embodiment O

The sensor of alternative embodiment A wherein said top face has araised region substantially surrounding said integral first surface.

Alternative Embodiment P

The sensor of alternative embodiment O further comprising a lid attachedto said raised region.

Alternative Embodiment Q

The sensor of alternative embodiment P wherein said lid is a rectangularplastic strip, said lid being attached to said raised region forming aplurality of vent openings.

Alternative Embodiment R

The sensor of alternative embodiment P wherein said lid is attached tosaid raised region and forms a capillary chamber.

Alternative Embodiment S

The sensor of alternative embodiment P wherein said lid is a hollowplastic frustum, having a large open end and a smaller closed end, saidsmaller closed end having a first surface with a plurality of ventholes.

Alternative Embodiment T

The sensor of alternative embodiment A wherein said top face istransparent.

Alternative Embodiment U

The sensor of alternative embodiment P wherein said top face istransparent or translucent, and said lid is opaque.

Alternative Embodiment V

The sensor of alternative embodiment A wherein said formed plastic bodyis porous, and further comprises a surfactant applied to said firstsurface.

Alternative Embodiment W

The sensor of alternative embodiment V wherein said porous plastic bodyis opaque.

Alternative Embodiment X

The sensor of alternative embodiment U wherein said formed plastic bodyhas a pore size of from about 5 microns to about 100 microns.

Alternative Embodiment Y

The sensor of alternative embodiment A wherein said first surface isconcave.

Alternative Embodiment Z

A fluid sensor comprising:

a formed porous plastic body having a top face with an integral firstsurface, a bottom face with a second surface opposed to said firstsurface, and a sidewall adjacent to said top face, wherein said firstsurface is adapted to accept a fluid sample;

a surfactant disposed on said body; and

a reagent adapted to reagent cause a color change detectable on saidsecond surface when said reagent reacts with an analyte in said fluidsample.

Alternative Embodiment AA

The sensor of alternative embodiment Z wherein said reagent is disposedon said second surface and said surfactant is applied to said firstsurface.

Alternative Embodiment BB

The sensor of alternative embodiment Z wherein said reagent is disposedon said first surface and said surfactant is applied to said secondsurface.

Alternative Embodiment CC

The sensor of alternative embodiment Z wherein said porous plastic bodyis opaque.

Alternative Embodiment DD

The sensor of alternative embodiment Z wherein said formed plastic bodyhas a pore size of from about 5 microns to about 100 microns.

Alternative Embodiment EE

The sensor of alternative embodiment Z wherein said top face has araised region substantially surrounding said integral first surface.

Alternative Embodiment FF

The sensor of alternative embodiment EE further comprising a lidattached to said raised region.

Alternative Embodiment GG

The sensor of alternative embodiment Z wherein said color change ismeasured by a change in reflectance on said bottom face.

Alternative Embodiment HH

The sensor of alternative embodiment GG wherein said reagent is aglucose dehydrogenase and pyrroloquinoline quinone-based system.

Alternative Embodiment II

The sensor of alternative embodiment HH wherein said reagent furthercomprises an electron transferring mediator, tetrazolium, and formazan.

Alternative Embodiment JJ

The sensor of alternative embodiment GG wherein said reagent is aglucose dehydrogenase and diaphorase-based system.

Alternative Embodiment KK

The sensor of alternative embodiment JJ wherein said reagent furthercomprises nicotinamide adenine dinucleotide, tetrazolium, and formazan.

Alternative Embodiment LL

The sensor of alternative embodiment II wherein said reagent is atitanium dioxide and polymer matrix.

Alternative Embodiment MM

The sensor of alternative embodiment KK wherein said reagent is atitanium dioxide and polymer matrix.

Alternative Embodiment NN

A blood glucose sensor kit comprising:

a) a sensor package having:1

i) a base portion having at least one sensor cavity and at least onedesiccant cavity in fluid communication with said sensor cavity,

-   -   ii) a desiccant material disposed within said desiccant cavity,    -   iii) a protective sheet covering said sensor cavity and said        desiccant cavity, and    -   iv) a sensor located in said sensor cavity;

b) a blood glucose meter having:

-   -   i) a housing,    -   ii) a display disposed on said housing, and    -   iii) a read-head disposed on said housing, said read-head being        adapted to detachably engage said sensor; and

c) a guide adapted to cover said protective sheet, said guide having atleast one opening adapted to align said read-head to engage said sensorwithin said sensor cavity.

Alternative Embodiment OO

The blood glucose sensor kit of alternative embodiment NN furthercomprising:

d) a removable blood glucose meter cover detachably mounted to saidblood glucose meter, said blood glucose meter cover having a recessadapted to contain said sensor package and said alignment guide.

Alternative Embodiment PP

The blood glucose sensor kit of alternative embodiment NN furthercomprising a lancet disposed on said housing of said blood glucosemeter.

Alternative Embodiment QQ

The blood glucose sensor kit of alternative embodiment NN wherein saidprotective sheet is thermoformed plastic film or aluminum burst foil.

Alternative Embodiment RR

The blood glucose sensor kit of alternative embodiment NN wherein saidsensor package includes a calibration label.

Alternative Embodiment SS

The blood glucose sensor kit of alternative embodiment NN wherein saidat least one sensor includes:

a formed porous plastic body, having a top face with an integral firstsurface, a bottom face with a second surface opposed to said firstsurface, and a sidewall adjacent to said top face, wherein said firstsurface is adapted to accept a fluid sample;

a surfactant disposed on said body; and

a reagent being disposed on said body and adapted to cause a colorchange detectable on said second surface when said reagent reacts withan analyte in said fluid sample.

Alternative Embodiment TT

The blood glucose sensor kit of alternative embodiment NN wherein saidat least one sensor includes:

a formed plastic body, having a top face with an integral first surface,a bottom face opposed to said first surface, and a sidewall extendingfrom the periphery of said top face, wherein said first surface isadapted to accept a fluid sample; and

a reagent being disposed on said integral first surface and adapted tocause a color change detectable on said second surface when said reagentreacts with an analyte in said fluid sample.

Alternative Embodiment UU

The blood glucose sensor kit of alternative embodiment NN wherein saidbase portion has a plurality of sensor cavities and at least onedesiccant cavity per sensor cavity in fluid communication with saidsensor cavity arranged in a rectangular array.

Alternative Embodiment VV

A blood glucose sensor kit comprising:

-   -   a) a sensor package having:        -   i) a container having an inner surface;        -   ii) a desiccant liner disposed in said container;        -   iii) a friction liner disposed in said container; and        -   iv) at least one sensor located in said container,            frictionally engaging said friction liner; and    -   b) a blood glucose meter having:        -   i) a housing,        -   ii) a display disposed on said housing, and        -   iii) a read-head disposed on said housing, said read-head            being adapted to detachably engage said sensor while said            sensor is located in said sensor package.

Alternative Embodiment WW

The blood glucose sensor kit of alternative embodiment VV wherein saidsensor package has a label affixed to an outer surface of saidcontainer, said blood glucose meter having a label marker disposed onsaid housing adapted to mark on said label the depth to which saidread-head is inserted into said container.

Alternative Embodiment XX

The blood glucose sensor kit of alternative embodiment VV wherein saidblood glucose meter further comprises a lancet disposed on said housing.

Alternative Embodiment YY

The blood glucose sensor kit of alternative embodiment VV furthercomprising a removable blood glucose meter cover detachably mounted tosaid blood glucose meter.

Alternative Embodiment ZZ

The blood glucose sensor kit of alternative embodiment VV wherein saidremovable blood glucose meter cover forms a recess adapted to containsaid sensor package.

Alternative Embodiment AAA

The blood glucose sensor kit of alternative embodiment VV wherein saidsensor package has a plurality of sensors stacked in an array.

Alternative Embodiment BBB

The blood glucose sensor kit of alternative embodiment VV wherein saiddesiccant liner is disposed on said inner surface of said container andwherein said friction liner is disposed on said desiccant liner.

Alternative Embodiment CCC

A blood glucose sensor package comprising:

-   -   a) a container having an inner surface;    -   b) a desiccant liner disposed in said container;    -   c) a friction liner disposed in said container;    -   d) a first sensor located in said container, frictionally        engaging said friction liner; and    -   e) a cover sealing said container.

Alternative Embodiment DDD

The blood glucose sensor package of alternative embodiment CCC furthercomprising a second sensor located in said container, wherein saidsecond sensor is stacked within said first sensor.

Alternative Embodiment EEE

The blood glucose sensor kit of alternative embodiment CCC wherein saiddesiccant liner is disposed on said inner surface of said container andwherein said friction liner is disposed on said desiccant liner.

Alternative Method FFF

A method of making a fluid sensor comprising the acts of:

a) forming a plastic body having a top face with an integral firstsurface, a bottom face opposed to said first surface, and a sidewallextending from the periphery of said top face, wherein said firstsurface is adapted to accept a fluid sample;

b) applying a reagent to said integral first surface, said reagent beingadapted to cause a color change detectable on said bottom face when saidreagent reacts with an analyte in said fluid sample; and

c) applying a lid to a raised region on said top face.

1-58. (canceled)
 59. A test sensor, comprising: a plastic body having atop portion and a sidewall extending from the periphery of the topportion, the top portion to accept a fluid sample; a reagent disposed onthe top portion to cause a detectable color change when the reagentreacts with an analyte in the fluid sample; and a lid coupled to theplastic body, the lid having a first open end and a second closed end.60. The test sensor of claim 59, wherein the second closed end of thelid forms a barrier to the reagent disposed on the top portion.
 61. Thetest sensor of claim 60, wherein the barrier formed by the lid is anopaque barrier.
 62. The test sensor of claim 61, wherein the secondclosed end of the lid includes a plurality of vent holes formed therein.63. The test sensor of claim 59, wherein the lid is coupled to theplastic body via sonic welding or an adhesive.
 64. The test sensor ofclaim 59, wherein the lid is coupled to the plastic body via a snap fitconnection.
 65. The test sensor of claim 59, wherein the lid includesimpermeable plastic.
 66. The test sensor of claim 59, wherein the lid isattached to the plastic body, thereby forming a capillary chamberbetween the lid and the top portion.
 67. The test sensor of claim 59,wherein the top portion is transparent and the lid is opaque.
 68. A testsensor, comprising: a plastic body having a top face with an integralfirst surface, a bottom face with a second surface opposed to the firstsurface, and a sidewall extending from the periphery of the top face,the integral first surface being configured to accept a fluid sample; areagent disposed on the integral first surface of the top face, thereagent to cause a detectable color change when the reagent reacts withan analyte in the fluid sample; and a lid coupled to the plastic bodysuch that the lid forms a barrier to the reagent disposed on theintegral first surface.
 69. The test sensor of claim 68, wherein thebarrier formed by the lid is an opaque barrier.
 70. The test sensor ofclaim 68, wherein the lid has a first open end and a second closed end.71. The test sensor of claim 70, wherein the second closed end of thelid includes a plurality of vent holes formed therein.
 72. The testsensor of claim 68, wherein the lid is coupled to the plastic body viasonic welding or an adhesive.
 73. The test sensor of claim 68, whereinthe lid is coupled to the plastic body via a snap fit connection. 74.The test sensor of claim 68, wherein the sidewall of the plastic bodyforms a protrusion, the lid including a groove that mates with theprotrusion on the sidewall of the plastic body when the lid is coupledto the plastic body.
 75. The test sensor of claim 68, wherein the lidincludes impermeable plastic.
 76. The test sensor of claim 68, whereinthe plastic body has a hollow frustum shape with a larger open end and asmaller closed end.
 77. The test sensor of claim 76, wherein the lid hasa hollow frustum shape with a larger open end and a smaller closed end.78. The test sensor of claim 68, wherein the lid is a rectangularplastic strip, the lid being coupled to the formed plastic body, therebyforming a plurality of vent openings.